When one gets into a discussion which is best, 8620, 4130 or 4150, one has reached a point where some intelligent barrel experience is needed. There are many technically good choices for a muzzle loading barrel. It does come down to exactly what is actually available. And then, well, gentlemen, what is the best brand of aged whiskey?
I have two rifles with Green Mountain barrels. Although I can't find it on their website, i have heard they use 1137MOD. I do not know what that "MOD" is, but surely it is a modification with less sulfur. Regular 1137 from some warehouse supply is not so ductile.
Over the last year or so I have revisited the subject of blown barrels, using stuff from the web. Most are illustrations of failed barrels in firearms other than side-lock muzzle loaders. The ones that split are resulfurized steel. They split because the sulfur is present as long strings - hopefully tiny - of manganese sulfide. This manganese sulfide makes the steel easier to machine, also gives it a "grain" somewhat like wood. As a very, very rough analogy, consider cross-cut vs rip saw. So the barrel, including many modern rifle barrels, is not so ductile in the cross-grain direction as it is in the long direction. "Stainless" is a rather general term, sometimes it means "416". This is a re-sulfurized stainless, and even then there is more than one variety of "416".
Sulfur as an addition to improve machinability has been around a lot longer than I have, at least well back into the 1930's or earlier.
As far as 12L14 is concerned. it gets really superb machinability because it has a phosphorus addition. Phosphorus dissolves in the steel, one cannot see it under the microscope. Phosphorus improves machinability because it makes steel Brittle. The chips are nice and crumbly, short. Not them there nasty long curls one gets when machining, say, 1018.
I think, not positive but pretty sure, the steel mills could not even make steel this brittle a steel until World War Two put great demands on productivity. 12L14 is truly a wonderful steel for making a lot of parts quickly. In Ancient Times I recall Black & Decker made drill chucks of the stuff, then case hardened them. Worked in the lab then, and I got a box full of broken parts every Wednesday to examine. I never saw a broken chuck. No doubt there must have been one, considering the interesting things customers did to their tools, but they happened not to send them back to B&D. 12L14 made a great drill chuck but not worth a #@$! for reliably containing an explosion.
Two subjects I'd comment on. Most, including myself from about 1968-198?, have had good luck with our 12L14 barrels. Thing is, all of those lucky barrels were made from bar stock that had no cracks in it. 12L14, however, is subject to cracking when the mill cold draws the hot rolled bar down to the nice perfectly round bar that will fit in a collet. Not often, but sometimes. If one has a cracked bar, well, it may work for quite a while. Or it may not. Especially if the new guy doesn't manage to get the ball all the way down in loading.
Loading errors? Come on now, we all know that firing with a short started ball is more common than one would prefer to admit. And each time, do you really get that ball all the way down on the powder? Does a newbie know how important this is?
Finally, it is NOT a matter of strength. 12L14 has much higher tensile strength than does wrought iron, when nice smooth bars are slowly pulled apart in a tensile test machine.
Not the issue. The steel must be ductile. This is something that late 19th century boiler makers slowly learned, after using this wonderful new, strong stuff called steel, instead of that nasty old weak wrought iron.
Whoops! The "strong" stuff didn't always hold together.
Someone here mentioned Spanish & Italian guns bulging. Yes, they bulge and eventually burst, but they do not shatter. This is because these Europeans are such fantastic machinists that they can actually make a barrel out of low sulfur steel. From what I've seen I think the Italian barrels are stronger (higher tensile strength!!! than the Spanish, but the Spanish barrels I've seen blown sure are ductile.
I like having ten fingers. I really prefer to have no sulfur addition to my gun barrels, thank you.
There is a very good thread here on shooting Zuoaves. I just got some .562 balls from TOW. Tuesday, weather permitting, I hope to give my slightly dinged up Zoli a try. Perfect bore.
